A digital power meter with a direct Internet access was developed based on the previously reported websensor concept. Line power is measured with a Cirrus Logic CS5460A single-phase bi-directional power-energy IC which has two analog inputs (150 m V RMS full scale), dual AID converters and a multiplier used to calculate true power and RMS voltage/current. Line voltage and current are scaled to the IC input with a voltage divider (1000:1) and a current shunt (5 mOmega), respectively. Binary data from the energy IC is transmitted to a microprocessor (PICmicro) which converts it into human readable (ASCII) form and sends it through the Esbus to a communication module, which reformats it into TCP/IP protocol format and transmits it over the Ethernet (Fig. 1). Up to 9 digital power meters may be connected on the optically isolated Esbus. The circuit, on 3 circuit boards, fits in a case which plugs into a standard wall socket (Fig. 2).
